This invention relates to freight load hauling on highway trailers, and more particularly to load covering arrangements for flatbed trailers.
Although a large amount of freight is containerized for trans-shipment via boat, rail, and highway, there is a great amount of freight that is shipped on flatbed trailers, in containers such as steel or plastic drums or barrels, pallet loads, custom packaging, or the like. These loads must be covered to prevent deterioration of the goods by the elements, protect the goods from vandals or thieves, and to provide safe vehicle operation.
There are known in the prior art many forms of load covering arrangements for flatbed trailers. In the simplest form, the loads are covered with tarps and tied down to cleats on the flatbed trailer. This approach requires a great deal of manual effort, and involves climbing up onto and down off of the flatbed trailer. Other more complex arrangements include tarp covers secured to a roller assembly extending above the trailer and aligned with the longitudinal axis thereof. The tarp covers may be supported by hoops or arches extending over the load area, or may include side edges received in channel guides. Conversely, some tarp covers rely on horizontally extending stays to define a shape for the tarp cover over the load area.
Roller mounted tarp covers suffer from drawbacks that have limited their utilization. There is no tarp fabric available that is sufficiently flexible and supple to be wrapped about a conveniently sized roller, yet strong enough to withstand extremely high wind exposure for prolonged periods, temperature extremes, prolonged wetting in hot and cold environments, and the like. Strengthening the fabric with stays creates a heavier tarp that requires a larger roller and roller driver.
A major drawback of roller mounted tarp covers is that although they provide positive retraction of the tarp cover, the roller assembly cannot by itself positively drive the tarp to unroll and extend outward and downward to enclose and cover the trailer. Rather, the unrolling action is created by manual traction applied to the lower edge of the tarp cover, aided by gravity. Thus physical effort is required to close the tarp cover, and operation is not automatic. Considering the long distances often spanned by tarp covers, one must be careful to pull the tarp cover straight down to avoid jamming the edges of the tarp on the channel guides (or the equivalent).
There is a need in the freight hauling industry for a retractable load cover for trailer-borne freight that requires minimal manual effort to retract or deploy, and which is strong, durable, and reliable.